Powered mechanical sweepers typically come in three sizes. The smallest size is used for sweeping sidewalks and factory floors. Operators of small sweepers may either walk behind the sweeper or ride on a small seat positioned behind the sweeping mechanism. Medium size sweepers are used for cleaning parking lots and small roads such as private roads or long driveways. Large sweepers are typically found on large public roads or on vast expanses of concrete surfaces such as found in commercial airports.
A medium size sweeper is one in which the sweeper is either pulled behind a tractor or where the sweeping equipment is mounted on the chassis of a small truck. The operator of a medium size sweeper will travel at road speeds to the location to be swept. Once at the location to be swept, the operator of the medium size sweeper engages the sweeping mechanism. With the sweeping mechanism engaged, the operator of the medium size sweeper uses the engine and transmission of either the tractor or small truck to control both the direction (forward and reverse) and speed of the sweeper when passing back and forth over the area to be swept. Speed control of the medium size sweeper over the surface being swept is typically accomplished by the foot pressure applied by the operator of the sweeper on the accelerator pedal or the foot brake to slow the sweeping vehicle using an automotive type friction braking system.
A large size powered sweeper typically includes a dedicated or modified truck chassis. However, the size of the areas to be swept, along with the type and quantity of debris expected to be encountered, necessitate the use of large brooms, large fans, and the capacity for picking up large pieces of debris along with a debris body for transporting a large amount of swept-up debris. One example of such a large sweeper is the VacAll™ Legacy model sweeper which is manufactured and marketed by the Gradall Division of the Alamo Group, the assignee of this U.S. Patent Application.
Because of the size of a large sweeper, as distinguished from a medium size sweeper, and the additional power needed to operate the sweeping equipment on large sweepers, prior art large sweepers have typically included two internal combustion engines. One internal combustion engine is the truck chassis engine. As on the medium size sweepers described above, the truck chassis engine is always mechanically connected to the chassis drive train. As will be well understood by those of ordinary skill in the art, attached to the chassis engine is a chassis transmission; typically, an automatic transmission. The chassis automatic transmission is connected by a driveshaft to the chassis differential and a rear wheel drive assembly. The chassis differential and the rear wheel assembly provide the power necessary to turn the rear wheels. The rear wheels propel the large sweeper to travel both at road speed to the location to be swept and then at sweeping speed over the surface being swept. Thus, whether traveling along a highway or working at a location that needs to be swept, the input by the operator of the sweeper to change the ground speed of the sweeper is by both placing foot pressure on the accelerator pedal to control the engine rpm and the selection of the gear in the chassis automatic transmission.
The second internal combustion engine in a large sweeper, typically referred to as an auxiliary engine, is usually mounted on the vehicle chassis behind the driver's compartment. This second internal combustion engine provides power to the sweeping equipment. When the large sweeper arrives at the large area, runway or road to be swept, the second internal combustion engine is put into operation. The operator of the vehicle with the sweeping equipment mounted thereon then drives the vehicle at a slow speed over the area to be swept.
The chassis internal combustion engine that comes with the vehicle chassis is used to propel large prior art sweepers using the chassis drive train. In some prior art sweepers, the sweeper moves too fast over the surface being swept. Accordingly, the operator of the sweeper must control the speed of the sweeper by maintaining continuous variable pressure on the brake pedal.
The second internal combustion engine is used to provide the power needed to operate all of the sweeping mechanisms. Unlike the chassis internal combustion engine, the second internal combustion engine typically bears an EPA rating as an off-road engine. The second internal combustion engine typically has its own cooling and air intake systems. The fuel tank and batteries for the second internal combustion engine are typically shared with the chassis internal combustion engine. Controls available to the operator provide for operating the variable speed broom motors and some of the sweeping functions; however, most everything regarding the sweeping operation runs at a speed directly proportional to the speed of the second internal combustion engine.
The disadvantages of operating a large sweeper having two internal combustion engines are the large amount of fuel consumed from the operation of two internal combustion engines, the wear and associated maintenance required to keep two internal combustion engines in operating condition as opposed to one internal combustion engine, and the noise and vibration from two internal combustion engines. Such noise and vibration has been shown to result in driver fatigue. In addition, since the brakes which are part of the vehicle chassis assembly are used to control the speed of the large sweeper in sweep mode, more frequent replacement of the brake pads, brake drums, or brake rotors on the wheel brakes is required.
Accordingly, there is a need for a large sweeper that reduces fuel consumption, reduces wear and maintenance, reduces noise and vibration, and does not require frequent replacement of parts of the wheel brake assemblies.
Attempts have been made to create a street cleaning vehicle with a single engine. One such example is shown in U.S. Pat. No. 6,073,720 to Vanderlinden. Therein, a power take-off from the chassis transmission is connected to a hydraulic pump. The hydraulic pump is connected to a hydraulic motor which is mounted on and is mechanically connected to the rear chassis differential. Power from the single chassis engine is also used to drive the sweeping equipment mounted on the chassis of the vehicle. Those of ordinary skill in the art will understand that the system disclosed in U.S. Pat. No. 6,073,720 to Vanderlinden requires modifying the chassis transmission and the rear chassis differential. Such modification of chassis components by a sweeper manufacturer is both expensive and typically voids the warranty on the chassis drive system components by the manufacturer of the vehicle chassis assembly. Because of these problems, the single engine sweeper proposed in U.S. Pat. No. 6,073,720 by Vanderlinden has not been generally accepted by the sweeper industry in the United States.
Thus, the need still remains in the art for a large sweeper having a single internal combustion engine. Those of ordinary skill in the art will understand that as more demands are put on a single internal combustion engine in a large sweeper, more control inputs are required of the vehicle operator to manage both the distribution of power between the vehicle and the sweeping equipment while guiding and controlling the speed and the direction of the large sweeper over the large area to be swept. Accordingly, there is an additional need to retain all of the advantages of a large vehicle chassis when not sweeping and to provide a separate system for controlling the speed of the vehicle when sweeping.